Archives of Acoustics, 35, 2, pp. 157-164, 2010

Sound-absorbing and insulating enclosures for ultrasonic range

Andrzej DOBRUCKI
Wrocław University of Technology, Institute of Telecommunications, Teleinformatics and Acoustics

Bronisław ŻÓŁTOGÓRSKI
Wrocław University of Technology, Institute of Telecommunications, Teleinformatics and Acoustics

Piotr PRUCHNICKI
Wrocław University of Technology, Institute of Telecommunications, Teleinformatics and Acoustics

Romuald BOLEJKO
Wrocław University of Technology, Institute of Telecommunications, Teleinformatics and Acoustics

The physical phenomena occurring in sound-absorbing and insulating enclosures are subject of the present paper. These phenomena are: absorption in air and by the sound-absorbing material covering the walls and the coincidence effect. The absorption in the air can be neglected in small size enclosures for low ultrasonic frequencies (20-30 kHz). The coincidence plays a role in decrease of the sound insulation, however the main role play the leaks. The boards made of ceramic fibers have been chosen as the optimal sound-absorbing material. They are dense and have deeply porous structures. The enclosure for insulation of 20-kHz noise produced by a welding machine has been designed and manufactured, and reductions of 25 dB of peak and Leq levels have been achieved.
Keywords: ultrasonic noise; sound absorbing and insulating enclosure; welder
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